1. Field of the Invention
The present invention relates to slide switch devices having a movable board for supporting a movable contact and a printed board for supporting a fixed contact with which the movable contact slidably contacts and, more particularly, to a slide switch device which is adapted to be immersed in automatic transmission oil or the like for automobiles.
2. Description of Prior Art
A conventional slide switch device adapted to be immersed in automatic transmission oil or the like is disclosed, for example, in Japanese Utility Model Unexamined Publication (Kokai) No. H4-65622. This conventional slide switch device has a fixed contact and a movable contact within a case enclosed by using an O-ring, and a rod movably supported by a bellows to have one end connected to the movable contact and the other end connected to a manual valve. With such structure, the movable contact is brought into contact with the fixed contact in a manner corresponding to the operational position of the manual valve.
In the above conventional structure, however, the fixed contact has a contact surface directed upward for the movable contact, and accordingly the fixed contact is apt to have foreign matters on the surface thereof. Consequently, where conductive foreign matters such as metal powder, and the like, are deposited on the surface of the fixed contact, there is a possibility of incurring troubles, such as poor insulation and the like. In particular, when used for an automatic transmission where oil temperature largely varies in dependence upon operating conditions of the engine, the air within the enclosed space will expand or contract. Furthermore, the operation of the rod and the bellows causes the difference of pressure between the space inside and the outside, thereby inducing the phenomenon of introducing oil into the enclosure space. As a result, there is a high possibility of introducing conductive foreign matters together with oil. Therefore, the conventional structure requires accommodation of the fixed contact and other components in a manner isolated from the outside. However, the complete enclosure of a case creates other problems in that the case is expensive to make and the structure is complicated.
Under such circumstances, the present applicant has previously proposed an in-liquid switch device which is adapted to have less deposits of conductive foreign matters on the surface of the fixed contact to prevent troubles, such as poor insulation or the like, even if used in a contaminated liquid having conductive foreign matters mixed therewith, such as an oil within an automatic transmission. In this proposed structure, the troubles of poor insulation and the like are eliminated, but there is still insufficient smoothness of sliding for the movable board.